Preparation Of Copper-based Nanoarray Electrocatalysts And Their Electrocatalytic Water Splitting Properties

The development of clean,low-carbon and sustainable new energy is an urgent need to solve environmental pollution and energy crisis.Hydrogen（H₂）is non-toxic,high energy density,and environmentally friendly,making it an ideal alternative to fossil fuels.Electrochemical hydrolysis is considered as a sustainable and promising method for large-scale production of H₂,which consists of two key reactions,namely oxygen precipitation reaction（OER）and hydrogen precipitation reaction（HER）.However,HER and OER reactions usually suffer from slow kinetics and high overpotential and require efficient electrocatalysts to accelerate the reactions.Noble metal-based catalysts（e.g.,Ru O₂,Ir O₂,Pt）have high catalytic activity and stability for OER and HER,but high cost and scarcity hinder their large-scale commercial application.Copper-based materials are considered as potential electrode materials due to their low cost,abundant reserves and different redox states.However,they have their own poor electrical conductivity,limited number of active sites,and low intrinsic activity.Therefore,in this thesis,the catalytic performance of copper-based materials was optimized by strategies such as morphology modulation,construction of heterogeneous structures and compounding with conductive substrates,and three copper-based electrocatalysts with multilayered core-shell nanoarray structures were developed and the reasons for their enhanced catalytic activity and durability were investigated.Details of the study are as follows:（1）Cu（OH）₂ nanorods were grown in situ on copper foam by anodic oxidation,and then Co S nanosheets were loaded onto Cu（OH）₂ nanorods by a simple electrodeposition method to synthesize Cu（OH）₂@Co S/CF electrocatalyst with a hierarchical core-shell nanoarray structure.Due to the synergistic effect of interfacial charge redistribution and multilayered hierarchical core-shell nanoarray structure,the Cu（OH）₂@Co S/CF catalysts possesses excellent OER catalytic activity.The overpotential was only 321 m V when the current density was 100 m A cm^-2,and the I-t test was performed at an overpotential of 280 m V,and the current density only decreased by 9.88%in 40 h,showing a good durability.（2）Cu nanorod arrays were fabricated on the surface of copper foam by anodic oxidation,annealing process and electrochemical reduction,and then multi-layered core-shell Cu@Ag@Co（OH）₂/CF nanoarray structures were synthesized by impregnation and electrodeposition methods.Due to the introduction of metal Ag in the construction of the multilayered core-shell structure,which modulates the electronic structure of the active sites of the catalyst and accelerates the electron transfer,while the multilayered core-shell nanoarray structure exposes more active sites,the catalyst has excellent OER performance and better stability in alkaline solution,and the current densities reach 30 and 100 m A cm^-2 at the overpotentials of279 and 324 m V,respectively,and its catalytic activity hardly decreased after 40 h of stability test.（3）Multilayered core-shell Cu_xO@Co O/CF nanoarray structures were synthesized on copper foam using anodic oxidation,hydrothermal method and annealing treatment under N₂ atmosphere,which exhibited excellent catalytic performance for OER and HER in alkaline solutions.In OER,the current densities reached 30 and 100 m A cm^-2 at overpotentials of 234 and 286 m V,respectively,while in HER the overpotential was only 178 m V at a current density of 10 m A cm^-2.The Cu_xO@Co O/CF catalyst,when used as anode and cathode,respectively,showed a cell voltage of only 1.637 V at a current density of 10 m A cm^-2,and their total decomposition water performance was superior to that of single Cu_xO/CF and Co O/CF.Through various characterization analyses,it was found that interfacial interactions were generated between Cu_xO and Co O,which could modulate the electron density and increase the charge transfer rate,thus accelerating the reaction kinetics.In addition,the catalyst is rich in oxygen vacancies,which can improve the reactivity of the active sites and optimize the adsorption energy of the reaction intermediates,thus enhancing the catalytic performance of the electrocatalyst.